Surgical stapling apparatus with locking mechanism

ABSTRACT

The present disclosure provides for a loading unit for use with and/or supportable on a distal end of a surgical stapling apparatus. The loading unit includes a housing portion including a distal end and a proximal end, a drive assembly slidably supported within the housing portion of the loading unit, and a locking mechanism supported on the housing portion of the loading unit. The locking mechanism has a first position wherein the locking mechanism engages the drive assembly and maintains the position of the drive assembly in a ready-to-load position relative to the housing portion of the loading unit. The locking mechanism is pivotable to a second position wherein the locking mechanism disengages the drive assembly and enables the drive assembly to move relative to the housing portion.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to U.S.Provisional Application Ser. No. 60/545,621, filed Feb. 17, 2004, theentire content of which being incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a surgical apparatus, e.g., a surgicalstapling apparatus. More particularly, the present disclosure relates toan endoscopic surgical stapling apparatus that includes a lockingmechanism for retaining the drive assembly of a loading unit, e.g., asingle use loading unit (“SULU”) or disposable loading unit (“DLU”), ata substantially fixed axial position until the SULU or DLU has beenloaded with or secured to a surgical stapling apparatus, to ensureproper or complete engagement of the SULU or DLU, especially its driveassembly, to the surgical stapling apparatus. For simplicity,hereinafter, SULU or DLU will be referred to as “DLU”, but it should beunderstood to include either or both a DLU or SULU.

2. Background of Related Art

Surgical devices wherein tissue is first grasped or clamped betweenopposing jaw structure and then joined by surgical fasteners are wellknown in the art. In some instruments a knife is provided to cut thetissue which has been joined by the fasteners. The fasteners aretypically in the form of surgical staples but two part polymericfasteners can also be utilized.

Instruments for this purpose can include two elongated jaw members whichare respectively used to capture or clamp tissue. Typically, one of thejaw members carries a staple cartridge which houses a plurality ofstaples arranged in at least two lateral rows while the other jaw memberhas an anvil that defines a surface for forming the staple legs as thestaples are driven from the staple cartridge. Generally, the staplingoperation is effected by cam members that travel longitudinally throughthe staple cartridge, with the cam members acting upon staple pushers tosequentially eject the staples from the staple cartridge. A knife cantravel between the staple rows to longitudinally cut and/or open thestapled tissue between the rows of staples. Such instruments aredisclosed, for example, in U.S. Pat. No. 3,079,606 and U.S. Pat. No.3,490,675.

A later stapler disclosed in U.S. Pat. No. 3,499,591 also applies adouble row of staples on each side of the incision. This patentdiscloses a surgical stapler that has a disposable loading unit in whicha cam member moves through an elongate guide path between two sets ofstaggered staple carrying grooves. Staple drive members are locatedwithin the grooves and are positioned in such a manner so as to becontacted by the longitudinally moving cam member to effect ejection ofthe staples from the staple cartridge of the disposable loading unit.Other examples of such staplers are disclosed in U.S. Pat. Nos.4,429,695 and 5,065,929.

Each of the instruments described above is designed for use inconventional surgical procedures wherein surgeons have direct manualaccess to the operative site. However, in endoscopic or laparoscopicprocedures, surgery is performed through a small incision or through anarrow cannula inserted through small entrance wounds in the skin. Inorder to address the specific needs of endoscopic and/or laparoscopicsurgical procedures, endoscopic surgical stapling devices have beendeveloped and are disclosed in, for example, U.S. Pat. No. 5,040,715(Green, et al.); U.S. Pat. No. 5,307,976 (Olson, et al.); U.S. Pat. No.5,312,023 (Green, et al.); U.S. Pat. No. 5,318,221 (Green, et al.); U.S.Pat. No. 5,326,013 (Green, et al.); U.S. Pat. No. 5,332,142 (Robinson,et al.); and U.S. Pat. No. 6,241,139 (Milliman et al.), the entirecontents of each of which are incorporated herein by reference.

Tyco Healthcare Group, LP, the assignee of the present application, hasmanufactured and marketed endoscopic stapling instruments, such as theMultifire ENDO GIA™ 30 and Multifire ENDO GIA™ 60 instruments, for anumber of years. These instruments include a surgical stapling apparatusand a DLU. Typically, the DLU is attached to the apparatus immediatelyprior to surgery. After use, the DLU can be removed from the apparatusand a new DLU can be fastened to the apparatus to perform additionalstapling and/or cutting operations. These instruments have providedsignificant clinical benefits. Nonetheless, improvements to theseinstruments are still possible.

It would be desirable to provide an improved DLU for a surgical staplingapparatus and an improved surgical stapling apparatus having the DLUloaded thereon.

It would also be desirable to provide a locking member for a DLU toassure proper loading of the DLU to the shaft of a surgical staplingapparatus.

Accordingly, it is an object of this disclosure to provide an improvedDLU which locks or retains its drive assembly in proper position to beloaded onto the shaft of a surgical stapling apparatus (hereinafterreferred to as the or a “ready-to-load position”) until the DLU isloaded onto a surgical stapling apparatus to assure that when the DLU isloaded thereto, the drive assembly is properly engaged by, coupled to orconnected to a drive member of the shaft, thereby helping to ensureproper operation of the DLU and the surgical stapling apparatus. Forexample, with the DLU loaded onto the surgical stapling apparatus, afterfiring of the surgical stapling apparatus, retraction of the control rodwill unapproximate or open and/or unclamp the anvil and cartridgeassemblies.

An object of the disclosure is to provide an improved DLU that includesa locking mechanism that retains the drive assembly in such aready-to-load position until the DLU is loaded onto the surgicalstapling apparatus.

Another object of the disclosure is to provide such a locking mechanismfor a DLU.

Another object of the present disclosure is to provide a lockingmechanism for a DLU and a DLU having a locking mechanism, such thatfiring of the surgical stapling apparatus is prevented unless and untilthe DLU is loaded onto the shaft of the surgical stapling apparatus.

Yet another object of the disclosure is to provide a DLU that, afterfiring, can be disconnected from the surgical stapling apparatus.

Yet another object of the disclosure is to provide a DLU that has onlytwo conditions, one in which it is not loaded and its drive assembly islocked or retained in the ready-to-load position, and another in whichthe DLU is loaded onto the shaft of a surgical stapling apparatus and inwhich the drive assembly is unlocked and free to be actuated.

Still another object of the present disclosure is to provide the aboveobjects in a roticulating, i.e., roticulable, DLU.

SUMMARY

In accordance with the present disclosure, a surgical apparatus, e.g., asurgical stapling apparatus, including a locking mechanism for ensuringproper engagement of a disposable loading unit to an end of the surgicalapparatus is provided. According to one aspect of the present disclosurethe surgical apparatus includes a housing, a handle supported by thehousing, and a loading unit supportable on a distal end of the housing.The loading unit includes a housing portion including a distal end and aproximal end, a drive assembly slidably supported within the housingportion of the loading unit, and a locking mechanism supported on thehousing portion of the loading unit. The locking mechanism has a firstposition in which the locking mechanism engages the drive assembly andmaintains the position of the drive assembly in a ready-to-load positionrelative to the housing portion of the loading unit. The lockingmechanism is movable, preferably pivotable in a plane substantiallytangential to an outer surface of the housing portion, to a secondposition in which the locking mechanism disengages the drive assemblyand enables the drive assembly to move relative to the housing portion.

Preferably, the locking mechanism includes a lever having a distal endpivotably connected to the housing portion and a free proximal end, anda tooth extending radially inward from the lever. Desirably, the toothselectively engages an engagement surface, e.g., a notch, formed in, onor of the drive assembly such that when the locking mechanism is in thefirst position the tooth engages the engagement surface of the driveassembly, and when the locking mechanism is in the second position thetooth is disengaged from the engagement surface of the drive assembly.

It is envisioned that when the locking mechanism is urged from the firstposition to the second position, the lever is pivoted about the distalend thereof such that a longitudinal axis of the lever is angled withrespect to a longitudinal axis of the housing portion. The lockingmechanism is preferably urged from the first position to the secondposition by a projection extending radially inward of the elongate body.Desirably, the projection acts on a side surface of the lever as theloading unit is twisted into loaded engagement in the elongate body.

Preferably, when the locking mechanism is in the first position thelever is substantially axially aligned with a nub extending radiallyoutward from the proximal end of the housing and when the lockingmechanism is in the second position the lever is out of axial alignmentwith the nub of the proximal end of the housing.

The proximal end of the lever can include a nub extending preferablyradially toward, the proximal end of the housing. The proximal end ofthe housing preferably includes a recess formed in the surface thereoffor receipt of the lever nub of the lever when the lever is in the firstposition.

The locking mechanism can further include a biasing member operativelyassociated therewith, wherein the biasing member tends to maintain thelever in the first position.

Preferably, the surgical apparatus is a fastener applier or stapler,preferably a laparoscopic or endoscopic stapler.

This disclosure also is of a DLU, preferably a roticulator DLU for asurgical fastener applier or stapler.

The surgical apparatus may further include an elongate body extendingfrom the housing.

It is further envisioned that the proximal end of the housing portion ofthe loading unit may define an insertion tip.

The present disclosure further provides for a loading unit for use withand/or supportable on a distal end of a surgical stapling apparatus. Theloading unit includes a housing portion including a distal end and aproximal end, a drive assembly slidably supported within the housingportion of the loading unit, and a locking mechanism supported on thehousing portion of the loading unit. The locking mechanism has a firstposition wherein the locking mechanism engages the drive assembly andmaintains the position of the drive assembly in a ready-to-load positionrelative to the housing portion of the loading unit. The lockingmechanism is pivotable, in a plane substantially tangential to an outersurface of the housing portion, to a second position wherein the lockingmechanism disengages the drive assembly and enables the drive assemblyto move relative to the housing portion.

Additional advantages will become apparent from the description whichfollows, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be further described with reference to theaccompanying drawings, wherein like reference numerals refer to likeparts in the several views, and wherein:

FIG. 1 is a top perspective view of a preferred embodiment of thepresently disclosed surgical stapling apparatus;

FIG. 2 is a top view of the surgical stapling apparatus shown in FIG. 1;

FIG. 3 is a side view of the surgical stapling apparatus shown in FIGS.1 and 2;

FIG. 4 is a top perspective view of the surgical stapling apparatus ofFIGS. 1–3 with the DLU disengaged from the elongate body of the surgicalstapling apparatus;

FIG. 5 is a bottom perspective view of a non-articulating DLU for usewith the surgical stapling apparatus of FIGS. 1–4;

FIG. 6 is a bottom perspective view of the preferred articulating DLU ofthe surgical stapling apparatus of FIGS. 1–4;

FIG. 7 is a top perspective view of the DLU of FIG. 6;

FIG. 8 is a top perspective view of the DLU of FIGS. 6 and 7;

FIG. 9 is a top perspective view, with parts separated, of the proximalhousing portion and mounting assembly of the DLU of FIGS. 6–8;

FIG. 10 is an enlarged top perspective view, with parts separated, of aproximal portion of the upper housing half of the DLU of FIGS. 6–9;

FIG. 11 is a top perspective view of the proximal housing portion andmounting assembly of the DLU of FIGS. 6–9 with the upper half of housingportion removed;

FIG. 12 is a top perspective view, with parts separated, of a portion ofthe axial drive assembly of the DLU of FIGS. 6–9;

FIG. 13 is a top perspective view of the portion of the axial driveassembly of FIG. 11 of the DLU of FIGS. 6–9;

FIG. 14 is an enlarged top perspective view of a lower housing half ofthe housing portion of the DLU of FIGS. 6–9;

FIG. 15 is an enlarged perspective view of the distal end of theelongated body of the stapling apparatus shown in FIGS. 1–4, shown withthe control rod extending therethrough;

FIG. 15 a is an enlarged perspective view of the distal end of theelongate body of FIG. 15, shown without the control rod extendingtherethrough;

FIG. 16 is an enlarged perspective view of the proximal end of the DLUof FIGS. 6–9 illustrating a locking mechanism according to the presentdisclosure;

FIG. 17 is an enlarged top plan view with portions broken awayillustrating a stage in the attachment of the DLU of FIGS. 6–9 to theelongate body of the surgical stapling apparatus shown in FIGS. 1–3;

FIG. 18 is an enlarged top plan view with portions broken awayillustrating another stage in the attachment of the DLU of FIGS. 6–9 tothe elongate body of the surgical stapling apparatus shown in FIGS. 1–3;

FIG. 19 is an enlarged top plan view with portions broken awayillustrating yet another stage in the attachment of the DLU of FIGS. 6–9to the elongate body of the surgical stapling apparatus shown in FIGS.1–3;

FIG. 20 is a longitudinal cross-sectional view of the proximal end ofthe DLU of FIGS. 6–9 as taken along line 20—20 of FIG. 16;

FIG. 21 is an enlarged transverse cross-sectional view of the proximalend of the DLU of FIGS. 6–9 with the distal end of the elongate body onthe proximal end of the DLU as would be taken along 21—21 of FIG. 16,illustrating the locking mechanism in the first position; and

FIG. 22 is an enlarged transverse cross-sectional view of the proximalend of the DLU of FIGS. 6–9 with the distal end of the elongate body onthe proximal end of the DLU as would be taken along 21—21 of FIG. 16,illustrating the locking mechanism in the second position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the presently disclosed surgical apparatus, DLUand locking mechanism or member will now be described in detail withreference to the drawings, in which like reference numerals designateidentical or corresponding elements in each of the several views.

In the drawings and in the description that follows, the term“proximal”, as is traditional, will refer to the end of the staplingapparatus which is closest to the operator, while the term “distal” willrefer to the end of the apparatus which is furthest from the operator.

FIGS. 1–4 show a surgical apparatus, e.g., surgical stapling apparatus,generally referred to as 10. In the interest of brevity, this disclosurewill focus primarily on systems, methods and structures for loading,engaging, coupling or connecting a disposable loading unit (“DLU”) 16 tosurgical stapling apparatus 10. A detailed discussion of the remainingcomponents and method of use of surgical stapling apparatus 10, isdisclosed in U.S. Pat. No. 6,241,139.

Surgical stapling apparatus 10 is an endoscopic apparatus and includes ahandle assembly 12 and an elongated body 14 extending from handleassembly 12. A DLU 16 is releasably secured to the distal end ofelongated body 14. While this disclosure relates to the use of a DLUwith surgical stapling apparatus 10, it is understood and within thescope of the present disclosure that a single use loading unit (SULU) orother end effector and/or tool assembly can equally be used incooperation with surgical stapling apparatus 10.

DLU 16 includes a tool assembly 17 having a cartridge assembly 18housing a plurality of surgical staples (not shown) and an anvilassembly 20 movably secured in relation to cartridge assembly 18. Asshown herein, DLU 16 is configured to apply six (6) linear rows ofstaples, each row in the DLU's measuring from about 30 mm to about 60 mmin length. DLUs for applying any number of rows of staples, havingstaple pockets arranged in various patterns and/or DLUs and endeffectors having any other lengths, e.g., 45 mm, are also envisioned.Handle assembly 12 includes a stationary handle member 22, a movablehandle member 24, and a barrel portion 26.

A rotatable member 28 preferably is mounted on the forward end of barrelportion 26 to facilitate rotation of elongated body 14 and attached DLU16 with respect to handle assembly 12. An articulation lever 30preferably is also mounted on the forward end of barrel portion 26adjacent rotatable member 28 to facilitate articulation of tool assembly17. Preferably, a pair of knobs 32 are movably positioned along barrelportion 26. Knobs 32 are advanced distally to approximate or closecartridge and/or anvil assembly 18, 20, and retracted proximally tounapproximate or open cartridge and/or anvil assembly 18, 20.

As seen in FIG. 4, DLU 16 is desirably selectively removably couplableto elongated body 14. DLU 16 includes a housing portion 200 having aproximal end adapted to releasably engage the distal end of elongatedbody 14. A mounting assembly 202 is pivotally secured at 203 to thedistal end of housing portion 200, and is configured to receive theproximal end of tool assembly 17 such that pivotal movement of mountingassembly 202 about an axis at 203 perpendicular to the longitudinal axisof housing portion 200 effects articulation of tool assembly 17.

FIGS. 5–8 show various perspective views of DLU 16. Surgical staplingapparatus 10 is capable of receiving a non-articulating DLU 16 a, asseen in FIG. 5, or an articulating DLU 16, as seen in FIGS. 6–8. U.S.Pat. No. 6,241,139 includes a detailed discussion of articulating andnon-articulating DLU.

With reference to FIGS. 9–14, DLU 16 includes a mounting assembly 235.Mounting assembly 235 includes an upper and a lower mounting portion236, 238, respectively. A centrally located pivot member 284 extendsfrom each of upper and lower mounting portions 236, 238 throughrespective openings 246 a formed in coupling members 246. Couplingmembers 246 each include an interlocking proximal portion 246 bconfigured to be received in grooves 290 formed in the distal end ofupper and lower housing halves 250, 252 to retain mounting assembly 235and upper and lower housing halves 250, 252 in a longitudinally fixedposition in relation to each other.

Upper housing half 250 and lower housing half 252 are contained withinan outer sleeve, shell or casing 251. The proximal end of upper housinghalf 250 includes an insertion tip 193 extending proximally therefrom.Insertion tip 193 includes engagement nubs 254, preferably a pair ofdiametrically opposed engagement nubs 254, extending radially outwardlytherefrom, for releasably engaging the distal end of body 14. Nubs 254form a bayonet-type coupling with the distal end of body 14. Housinghalves 252 and 254 define a channel 400 for slidably receiving axialdrive assembly 212 therein. An articulation link 256 is dimensioned tobe slidably positioned within a slot 402 formed in upper and lowerhousing halves 250, 252. A pair of blow out plate assemblies 255 arepositioned adjacent the distal end of housing portion 200 adjacent thedistal end of axial drive assembly 212 to prevent outward buckling andbulging of drive assembly 212 during articulation and firing of surgicalstapling apparatus 10. For a detailed discussion of the structure andoperation of blow out plate assemblies 255, reference is made toInternational Application Serial No. PCT/US02/32031, filed on Oct. 4,2002, entitled “Surgical Stapling Device”, the entire content of whichis herein incorporated by reference.

Referring to FIG. 9, optionally, a locking member 288 may be supportedon engagement section 270 of axial drive assembly 212. In operation,when axial drive assembly 212 is actuated, by applying a predeterminedforce to movable handle member 24 to advance axial drive assembly 212distally, locking member 288 provides an audible and tactile indicationthat surgical stapling apparatus 10 has been actuated. For a detaileddiscussion of the structure and operation of locking member 288,reference is made to the aforementioned International Application SerialNo. PCT/US02/32031. Locking member 288 may also prevent inadvertentpartial actuation of DLU 16, such as during shipping, by locking axialdrive assembly 212 at a fixed position within DLU 16 until apredetermined axial force has been applied to axial drive assembly 212.

With reference to FIGS. 9–12, axial drive assembly 212 includes anelongated drive beam 266 (FIGS. 11 and 12) including a distal workinghead 268 (FIGS. 11 and 12) and a proximal engagement section 270. Drivebeam 266 may be constructed from a single sheet of material or,preferably, multiple stacked sheets, as shown in FIG. 11. Engagementsection 270 includes a pair of resilient engagement fingers 270 a and270 b which are dimensioned and configured to mountingly engage a pairof corresponding retention slots 272 a and 272 b formed in drive member272 (FIGS. 11 and 13). Drive member 272 includes a proximal porthole 274configured to receive distal end 276 of a drive member, e.g., drive rodor control rod 52 (FIGS. 15 and 20–22) when the proximal end of DLU 16is being engaged with elongated body 14 of surgical stapling apparatus10. Control rod 52 functions to impart axial movement of drive assembly212 from handle assembly 12.

As seen in FIGS. 9, 10 and 16–22, DLU 16 further includes a lockingmechanism 300, preferably, pivotably supported on upper housing half250. Locking mechanism 300 is manipulatable from a first position, inwhich drive assembly 212 is maintained in a ready-to-load position, to asecond position, in which drive assembly 212 is free to move. DLU 16 isconsidered to be loaded to elongate body 14 when locking mechanism 300is in the second position, i.e., when drive assembly 212 is connected tocontrol rod 52 of elongate body 14. Locking mechanism 300 includes alever 302 including a distal end 304 pivotally connected to upperhousing half 250 and a free proximal end 306 in operative associationwith an outer surface of insertion tip 193. Desirably, distal end 304 ispivotably connected to upper housing half 250, via a pin 308 orpreferably a ball-type pivot member. Alternatively, other known pivotstructures formed integrally with or separate from upper housing half250 may be used. Lever 302 further includes a projection, here shown asa tooth 310, extending radially inwardly from the inner surface of lever302, preferably at a location between distal end 304 and proximal end306.

In use, as best seen in FIGS. 16–22, when locking mechanism 300 is inthe first position (i.e., in a ready-to-load, locked, or coupledposition) (FIGS. 16, 17, 18, 20 and 21), lever 302 is substantiallyaxially aligned with a longitudinal axis of housing portion 200 suchthat tooth 310 passes through an aperture 250 a formed in upper housinghalf 250 and is engaged with an engagement surface, e.g., a notch,shoulder or recess 270 c formed in the edge of engagement section 270 ofdrive assembly 212 to thereby effectively lock and maintain driveassembly 212 in the ready-to-load position wherein drive assembly 212 isin a retracted or proximal-most position relative to upper housing half250. When DLU 16 is being coupled to the distal end of body 14, lockingmechanism 300 ensures that engagement section 270 of drive assembly 212is in a position to and properly engages, coupled with or connects todistal end 276 of control rod 52 (see FIGS. 20–22) of surgical staplingapparatus 10. Distal end 276 of control rod 52 has one or moreengagement surfaces, preferably, and here shown as, including a head 276a and a smaller diameter annular recess 276 b just proximal of head 276a and partially defined by head 276 a. Thereafter, less preferablyconcomitantly therewith, locking mechanism 300 is manipulated (hererotated) to the second position wherein drive assembly 212 is in anunlocked, operative position in which lever 302 is angled with respectto the longitudinal axis of housing portion 200 such that tooth 310 isreleased from and/or otherwise disengaged from engagement surface 270 cof engagement section 270 of drive assembly 212 to free drive assembly212 to move relative to housing portion 212, here, upper and lowerhousing portion 250, 252 of DLU 16.

When locking mechanism 300 is in the second position, DLU is consideredloaded onto ad/or into elongate body 14 of surgical stapling apparatus10. Thus, drive assembly 212 is free to be actuated and reciprocatedaxially by drive rod 52 to perform its operative functions ofapproximating and closing anvil and cartridge assemblies 18, 20, drivingknife 280 and firing staples, as well as of un-approximating,un-clamping, and retracting drive assembly 212. DLU 16 is considered tobe loaded to elongate body 14 when locking mechanism 300 is in thesecond position, i.e., when drive assembly 212 is connected to controlrod 52 of elongate body 14.

With continued reference to FIGS. 15–20, preferably lever 302 of lockingmechanism 300 further includes a nub or detent 314 extending radiallyinward from an inner surface 302 a of distal end 306 of lever 302. Inuse, nub 314 selectively engages and disengages a recess or dimple 193 aformed in the outer surface of insertion tip 193. Preferably, dimple 193a is substantially in axial alignment with nubs 254 extending radiallyoutward from insertion tip 193. Nub 314 and dimple 193 a create asnap-fit type engagement wherein nub 314 and dimple 193 a cooperate withone another to prevent and/or otherwise inhibit locking mechanism 300from inadvertently or prematurely pivoting from the first position tothe second position and thereby disengaging drive assembly 212. Lockingmechanism 300 thus can include nub 314 and dimple 193 a.

Preferably, insertion tip 193 includes a recessed area 193 b (FIGS. 10and 16) formed therein such that locking mechanism 300 does not extendradially outward beyond the outer surface of upper housing half 250.Lever 302 is able to pivot an amount sufficient to allow tooth 310 todisengage engagement surface or shoulder 270 c of engagement section 270of drive assembly 212 when locking mechanism 300 is in the secondposition. Locking mechanism 300 preferably includes a spring or otherbiasing means 312 in operative association with lever 302 and housingportion 200 mounted and/or positioned in such a manner so as to biaslever 302 to the first position. As seen in FIG. 16, spring 312 includesan arm 312 a in contact with a side surface 302 a of lever 302 therebytending to maintain lever 302 in the first position. The twisting forceapplied with respect to DLU 16 and/or elongate body 14 of surgicalstapling apparatus 10 is sufficient to overcome the bias of spring 312to allow lever 302 to move to the second position.

With continued reference to FIGS. 15–20, a method of use and/oroperation of locking mechanism 300, in securing DLU 16 to the distal endof elongate body 14, will be discussed. Initially, with lockingmechanism 300 in the first position such that tooth 310 is in lockingengagement with shoulder 270 c of engagement section 270, to ensure thatdrive assembly 212 is in the proper position (e.g., in the proximal-mostposition) for coupling with head 276 a of distal end 276 of control rod52, insertion tip 193 of DLU 16 is introduced longitudinally into thedistal end of elongate body 14, in the direction of arrow “A”, such thatnubs 254 slide into channels 276 d, through and past projections 276 c(see FIGS. 15 and 15 a) extending radially inward from elongate body 14of surgical stapling apparatus 10 near the distal end thereof.

When nubs 254 have reached slots 276 e, and when insertion tip 193 hasbeen fully inserted into the distal end of elongate body 14, DLU 16 isrotated, in the direction of arrow “B” (see FIG. 21). At this point inthe coupling, rotation of DLU 16 results in three separate actions,namely, nubs 254 enter slots 276 e, thus connecting DLU 16 to distal end14 of stapling apparatus 10; projections 276 b of firing rod 52 engagesections 270 a and 270 b of drive assembly 212, thus connecting firingrod 52 and drive assembly 212; and side wall of channel 276 d urgeslever 302 (such that side wall of channel 276 d abuts against andengages proximal end of lever 306, preferably against a side surface 302b of lever 302) of locking mechanism 300 to pivot from the firstposition to the second position about pivot pin “P” to thereby disengagetooth 310 from shoulder 270 c of engagement section 270 and thereby freedrive assembly 212 to allow movement of drive assembly 212 and permitoperation or continued operation of surgical stapling apparatus 10.

As can be appreciated, if lever 302 has been inadvertently moved to thesecond position, prior to coupling of DLU 16 to elongate body 14, anddrive assembly 212 has prematurely moved from its proximal-most orready-to-load position, lever 302 can not move to the first positionsince tooth 310 is not aligned with drive assembly 212 and can not passin front of shoulder 270 c. In such a situation, tooth 310 will abutagainst a portion of engagement section 270 to prevent lever 302 fromreturning to the first position. Thus, upon insertion of DLU 16 intoelongate body 14, proximal end 306 of lever 302 will abut against and/orotherwise contact projection 276 c of elongate body 14 and thus preventloading of DLU 16 to elongate body 14.

Accordingly, the attachment of a DLU having a drive assembly which isnot in its proximal-most or ready-to-load position is prevented.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplifications ofpreferred embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the claims appended hereto.

1. A surgical apparatus comprising: a housing; a handle supported by thehousing; and a loading unit supportable on a distal end of the housing,the loading unit including: a housing portion including a distal end anda proximal end; a drive assembly slidably supported within the housingportion of the loading unit; and a locking mechanism pivotally supportedon the housing portion of the loading unit, the locking mechanism havinga first position wherein the locking mechanism engages the driveassembly and maintains the position of the drive assembly in aready-to-load position relative to the housing portion of the loadingunit, the locking mechanism being pivotable, in a plane substantiallytangential to an outer surface of the housing portion, to a secondposition wherein the locking mechanism disengages the drive assembly andenables the drive assembly to move relative to the housing portion. 2.The surgical apparatus of claim 1, wherein the locking mechanismincludes: a lever having a distal end pivotably connected to the housingportion and a free proximal end; and a tooth extending radially inwardfrom the lever, wherein the tooth selectively engages an engagementsurface formed on the drive assembly such that when the lockingmechanism is in the first position the tooth engages the engagementsurface of the drive assembly and when the locking mechanism is in thesecond position the tooth is disengaged from the engagement surface ofthe drive assembly.
 3. The surgical apparatus of claim 2, wherein whenthe locking mechanism is moved from the first position to the secondposition, the lever is pivoted about the distal end thereof such that alongitudinal axis of the lever is angled with respect to a longitudinalaxis of the housing portion.
 4. The surgical apparatus of claim 3,wherein the locking mechanism is moved from the first position to thesecond position by a projection extending radially inward of theelongate body, the projection acting on a side surface of the lever asthe loading unit is twisted into loaded engagement in the elongate body.5. The surgical apparatus of claim 4, wherein when the locking mechanismis in the first position the lever is substantially axially aligned witha nub extending radially outward from the proximal end of the housingportion and when the locking mechanism is in the second position thelever is out of axial alignment with the nub of the insertion tip. 6.The surgical apparatus of claim 5, wherein the proximal end of the leverincludes a nub extending toward the proximal end of the housing portion,and wherein the proximal end of the housing portion includes a recessformed in the surface thereof for receipt of the nub of the lever whenthe lever is in the first position.
 7. The surgical apparatus of claim6, wherein the locking mechanism further includes a biasing memberoperatively associated therewith, wherein the biasing member tends tomaintain the lever in the first position.
 8. The surgical apparatus ofclaim 7, wherein the surgical apparatus is a stapler.
 9. The surgicalapparatus of claim 8, further comprising an elongate body extending fromthe housing.
 10. The surgical apparatus of claim 9, wherein the proximalend of the housing portion of the loading unit defines an insertion tip.11. A loading unit for use with and/or supportable on a distal end of asurgical stapling apparatus, the loading unit comprising: a housingportion including a distal end and a proximal end; a drive assemblyslidably supported within the housing portion of the loading unit; and alocking mechanism pivotally supported on the housing portion of theloading unit, the locking mechanism having a first position wherein thelocking mechanism engages the drive assembly and maintains the positionof the drive assembly in a ready-to-load position relative to thehousing portion of the loading unit, the locking mechanism beingpivotable, in a plane substantially tangential to an outer surface ofthe housing portion, to a second position wherein the locking mechanismdisengages the drive assembly and enables the drive assembly to moverelative to the housing portion.
 12. The loading unit of claim 11,wherein the locking mechanism includes: a lever having a distal endpivotably connected to the housing portion and a free proximal end; anda tooth extending radially inward from the lever, wherein the toothselectively engages an engagement surface formed on the drive assemblysuch that when the locking mechanism is in the first position the toothengages the engagement surface of the drive assembly and when thelocking mechanism is in the second position the tooth is disengaged fromthe engagement surface of the drive assembly.
 13. The loading unit ofclaim 12, wherein when the locking mechanism is moved from the firstposition to the second position, the lever is pivoted about the distalend thereof such that a longitudinal axis of the lever is angled withrespect to a longitudinal axis of the housing portion.
 14. The loadingunit of claim 13, wherein the locking mechanism is moved from the firstposition to the second position by a projection extending radiallyinward of the elongate body, the projection acting on a side surface ofthe lever as the loading unit is twisted into loaded engagement in theelongate body.
 15. The loading unit of claim 14, wherein when thelocking mechanism is in the first position the lever is substantiallyaxially aligned with a nub extending radially outward from the proximalend of the housing portion and when the locking mechanism is in thesecond position the lever is out of axial alignment with the nub of theproximal end of the housing portion.
 16. The loading unit of claim 15,wherein the proximal end of the lever includes a nub extending towardthe proximal end of the housing portion, and wherein the insertion tipincludes a recess formed in the surface thereof for receipt of the nubof the lever when the lever is in the first position.
 17. The loadingunit of claim 16, wherein the locking mechanism further includes abiasing member operatively associated therewith, wherein the biasingmember tends to maintain the lever in the first position.
 18. Theloading unit of claim 17, wherein the loading unit functions as asurgical stapler.
 19. The loading unit of claim 18, wherein the proximalend of the housing portion of the loading unit defines an insertion tip.